This application represents a continuation of our efforts on the basic understanding of the biochemistry of fibrinolysis. In this renewal, we intend to purify and characterize plasminogen activators from various sources, to obtain various chemically modified plasminogens, and plasminogen active fragments, and to examine their activation capabilities, binding of antifibrinolytic amino acids, binding to fibrinogen and fibrin. We also intend to further our biochemical understanding of the activation of plasminogens from various sources by streptokinase, urokinase, and other activators. Finally, we will examine the role of the carbohydrate in the various physical and chemical properties of plasminogen and plasmin, and attempt to understand the nature of the active site of plasmin.